1. Field of the Invention
The present invention relates to the field of biological assays and apparatus for carrying out such assays, such as a microfluidic device, to which is applied electric fields to control movement of charged molecules. The assays involve charged molecular species, such as nucleotides (due to phosphate ions), or other molecules which contain a charge due to their ionic nature, such as certain proteins or small molecules.
2. Related Art
Advances in silicon microfabrication have been used to produce microchannels and microarrays for many lab-on-a-chip platforms. Advantages include low reagent costs, miniaturization, and fast reaction rates. However, the challenge is to efficiently isolate and deposit biological samples into individual wells for high-throughput analysis. Recently, random arrays have been implemented in which solid-supports are used to individually capture unique biological molecules and deposit these solid supports into reaction wells with a geometry of the same size range. Another challenge these platforms are faced with is when repetitive assay are performed on the same bead isolated within a well. A good example where these challenges are common is DNA sequencing.
In certain methods of DNA sequencing, DNA is immobilized on a solid support, and nucleotides and enzymes are delivered to the DNA for successive incorporation of nucleotides. This is commonly referred to as DNA sequencing using sequencing-by-synthesis. Nucleotides are removed through washing to allow iterative nucleotide addition. One of the main challenges in sequencing by synthesis is to deliver the nucleotide to the vicinity of DNA to enable rapid incorporation and to remove the nucleotide efficiently to enhance the read-length.